1. Field of the Invention
The invention relates to a thermosetting adhesive based on a reactive acrylate and/or methacrylate copolymer.
2. Description of the Prior Art
German Pat. No. 25 24 197 discloses adhesives composed of a terpolymer, consisting of
20 to 45 weight percent of acrylonitrile and/or methacrylonitrile, PA0 45 to 70 weight percent of an alkyl acrylate with 1 to 12 carbon atoms in the alkyl radical and PA0 the sum of the monomers amounting to 100 weight percent and the copolymer obtained having a limiting viscosity of 0.1 to 0.8 (100 ml.multidot.g.sup.-1) at 20.degree. C. in chloroform, optionally in admixture with up to 35 weight percent of an epoxide resin or a phenol-formaldehyde resin containing glycidyl groups. PA0 (a) 20 to 80 weight percent of a copolymer with was obtained by the polymerization of PA0 (b) 10 to 70 weight percent of an epoxide resin and/or a phenol-formaldehyde resin containing glycidyl groups, PA0 (c) 0.2 to 15 weight percent of a hardener for the components (b), which is effective at elevated temperatures, PA0 (d) 0 to 5 weight percent of an accelerator for the reaction of components (b) with components (a) and (c), PA0 the sum of (a) to (d) amounting to 100 weight percent, and optionally the usual additives, such as, gluing auxiliaries, adhesion promoters, pigments and fillers. PA0 (a) a copolymer, which is obtained by the polymerization of PA0 (b) one or more polyisocyanates and/or their partial reaction products with polyols, the molecule having at least 2 isocyanate groups on the average, wherein PA0 components (a) and (b) being present in a ratio such that one hydroxyl group of component (a) corresponds to 1 to 1.5 isocyanate groups of component (b). The composition may also optionally contain conventional additives, such as, accelerators, gluing auxiliaries, pigments and fillers.
1 to 10 weight percent of acrylic, methacrylic or itaconic acid, wherein
These adhesives make glue bonds of high tensile shear strength and good peel strength possible. The adhesive can be used as films for gluing metal surfaces and also for gluing plastic film to metal surfaces. If these adhesives do not contain epoxide resins or phenol-formaldehyde resins containing glycidyl groups, they remain thermoplastic. In the presence of epoxide resins or phenol-formaldehyde resins containing glycidyl groups, the adhesives are thermosetting with temperatures of about 130.degree. C. being required for the curing.
In German patent application No. P 29 26 284.8-43, which has not yet been published, a thermosetting adhesive is described which contains the following active components:
(a.sub.1) 20 to 45 weight percent of acrylonitrile and/or methacrylonitrile, PA1 (a.sub.2) 35 to 65 weight percent of one or several alkyl esters of acrylic and/or methacrylic acid with 1 to 12 carbon atoms in the alkyl radical, PA1 (a.sub.3) 10 to 20 weight percent of acrylic, methacrylic and/or itaconic acid, PA1 (a.sub.4) 0 to 15 weight percent of acrylamide and/or methacrylamide, PA1 the sum of the monomers amounting to 100 weight percent and the copolymer having a limiting viscosity of 0.1 to 0.8 (100 ml.multidot.g.sup.-1) at 20.degree. C. in methyl acetate, PA1 (a.sub.1) 35 to 70 weight percent of one or several alkyl esters of acrylic and/or methacrylic acid with 1 to 8 carbon atoms in the alkyl radical, PA1 (a.sub.2) 20 to 45 weight percent of acrylonitrile and/or methacrylonitrile and/or vinyl acetate, PA1 (a.sub.3) 10 to 20 weight percent of one or several .omega.-hydroxyalkyl esters of acrylic and/or methacrylic acid with 1 to 5 carbon atoms in the alkyl radical, PA1 (a.sub.4) 0 to 15 weight percent of acrylamide and/or methacrylamide, and PA1 (a.sub.5) 0 to 35 weight percent of acrylic or vinyl monomers, whose composition is different from that of the components of (a.sub.1) to (a.sub.4), PA1 the sum of the monomers (a.sub.1) to (a.sub.5) amounts to 100 weight percent and the copolymer has a limiting viscosity of 0.05 to 0.6 (100 ml.multidot.g.sup.-1) at 25.degree. C. in methyl acetate; and
Compared to the adhesives of German Pat. No. 25 24 197, these adhesives cure at temperatures of 100.degree. C. to 130.degree. C. Consequently, it is possible to keep the thermal stress on the plastics to be glued at a lower level and to retain desirable properties, such as, the surface quality and gloss of the plastics. The composite materials of plastic and metal, obtained by the gluing, can be molded in the usual manner without impairing the adhesion.